1. Field of the Invention
The present invention relates to a control system for a liquefied gas container, such as a low-temperature controlled vessel.
2. Description of the Prior Art
For measuring the extremely weak intensity of magnetic fields arising from organisms, such as a human brain, arm, eyeball, or heart, there has been used a superconductive quantum interference device (hereafter referred to as a SQUID) comprising in combination a superconductive ring and one or two Josephson junctions, which SQUID is immersed in a liquefied helium gas within a low-temperature controlled vessel. There is no known arrangement for controlling the temperature of the liquefied helium gas in such a low-temperature controlled vessel within a precise range of, for example, 4.2.degree..+-.0.1.degree.K. In order to attain a high precision measurement with a SQUID, it is necessary to maintain the temperature of the liquefied gas at a constant level within close limits.